Over the last few decades, much research has focused on the production of recombinant proteins, e.g. monoclonal antibodies, and the work has taken a variety of angles. While much work in the literature has utilized media containing sera or hydrolysates, chemically defined media were also developed in order to eliminate the problematic lot-to-lot variation of complex components (Luo and Chen, Biotechnol. Bioeng. 97(6):1654-165.9 (2007)). An improved understanding of the cell culture has permitted a shift to chemically defined medium without compromising on growth, viability, titer, etc., To date optimized chemically defined processes have been reported with titers as high as 7.5-10 g/L (Huang et al., Biotechnology Progress 26(5):1400-1410 (2010); Ma et at, Biotechnol. Prog. 25(5):1353-1363 (2009); Yu et al.; Biotechnol. Bioeng. 108(5):1078-1088 (2011)). In general, the high titer chemically defined processes are fed batch processes with cultivation times of 11-18 days. The process intensification has been achieved without compromising product quality while maintaining relatively high viabilities.
Achievement of a robust, scalable production process includes more than increasing the product titer while maintaining high product quality. The process must also predictably require the main carbohydrate source such that the feeding strategy does not need to change across scales. As many processes use glucose as the main carbohydrate, and have lactate and ammonium as the main byproducts, the time course of these three critical chemicals should also scale.
A recent metabolomics study performed by Ma and coworkers (Ma et al., Biotechnol. Prog. 25(5):1353-1363 (2009)) suggested a blockage in the TCA cycle, resulting in an early phase secretion of citrate and later citrate consumption. The process used by Ma may also have subsequently resulted in high LPR: if the viability permitted further extension of the process. The feeding of pyruvate (0.02 M) was shown to increase antibody production by 43% in a continuous culture of a hybridoma cell (Omasa et al., Bioproc. Biosys. Engin. 33(1):117-125 (2010)). The feeding of citrate (0.05 M and 0.01 M) in the same culture system resulted only in a ˜5-10% increase in antibody production. Bai recently reported increased antibody production in a chemically defined CHO cell culture supplemented with a combination of high concentrations of chemically defined iron and high concentrations of citrate (Bai et al., Biotechnol. Prog. 27(1):209-219 (2011)). Citrate supplementation alone, however, could not support stable cell growth at all.
There is a need in the art to further improve recombinant protein production processes to eliminate lot-to-lot metabolic variability. Provided herein are compositions and methods to prevent or reduce metabolic variability encountered in recombinant protein producing cell cultures.